Method of temporarily accessing the interior of a wind turbine blade

Abstract

The disclosed method involves accessing the interior of a wind turbine blade by creating a temporary access window by removing a portion of the blade shell in the airfoil region at a chordwise distance from the spar caps. This allows operators to perform tasks, such as repairs or retrofitting, within the blade's interior. After task completion, precured plug components are inserted into the access windows from the exterior and irreversibly secured to the blade shell, effectively closing the temporary access window.

Description

[0001] P2612PC00 (701356-WO-l)

[0002] 1

[0003] METHOD OF TEMPORARILY ACCESSING THE INTERIOR OF A WIND TURBINE BLADE

[0004] FIELD OF THE INVENTION

[0005] The present invention relates to a method of establishing and subsequent closing of a temporary access window to the interior of a finished wind turbine blade for inspection, testing, or modifying interior components of the blade.

[0006] BACKGROUND

[0007] Wind turbine blades are critical components in modern wind energy systems, designed to capture kinetic energy from wind and convert it into electrical energy. Traditional wind turbine blades have a complex internal structure, typically including spar caps and shear webs, to provide the necessary strength and rigidity. Wind turbine blades are typically large structures, today exceeding a hundred metres, and occasionally requiring maintenance or modifications after installation, such as for structural reinforcements or sensor installations.

[0008] In the existing technology, temporarily accessing the interior of wind turbine blades for maintenance or repair purposes often involves labour-intensive processes. Some solutions involve removing a shell section from the rotor blade shell to create an access window. After the necessary internal modifications are made, the removed section reseals the access window. While this method allows for interior access, it requires the careful removal of significant portions of the blade shell, which can compromise structural integrity and lead to increased labour and material costs.

[0009] Furthermore, the shell section must be removed from the rotor blade shell in a manner that preserves its integrity. The process must ensure that a substantial portion of the shell section remains intact to facilitate its reuse when sealing it back to the rotor blade. This necessity imposes constraints on the removal process, demanding precision and care to avoid damaging the shell section. Such constraints can complicate the maintenance procedure, increase the complexity and time required for the task, and potentially lead to additional material costs if the shell section is damaged and cannot be reused as intended.

[0010] A further difficulty involves ensuring a high-quality bond between the shell section and the remainder of the blade shell after interior maintenance or modifications. Achieving a seamless reintegration of the shell section is critical for maintaining the structural integrity and aerodynamic efficiency of the wind turbine blade. However, variations in cutline thickness and the tight tolerances required for the shell section's fit can complicate this process. Inconsistent or imprecise cuts may lead to gaps or misalignments, which can weaken the bond and potentially compromise the blade's performance. These challenges necessitate meticulous attention to detail and precision during both the cutting and resealing processes, adding complexity and time to maintenance operations. P2612PC00 (701356-WO-l)

[0011] 2

[0012] Depending on the circumstances, establishing a temporary access may even be performed up-tower, i.e. while the wind turbine blade is attached to the hub. The above difficulties are further amplified when maintenance is carried out up-tower, where restricted access and challenging working conditions exacerbate the risk of structural compromise and significantly increase the labour and time required for maintenance activities. Additionally, when such maintenance is performed up- tower, the wind turbine must be brought to a standstill, resulting in production losses due to the halt in energy generation, further exacerbating the economic impact of the maintenance process.

[0013] SUMMARY OF THE DISCLOSURE

[0014] It is an object of the present disclosure to provide an improved method for accessing the interior of wind turbine blades that mitigates the drawbacks of the prior art, such as structural compromise and labour intensity, while facilitating efficient inspection and modification tasks.

[0015] A first aspect of the present disclosure relates to a method of accessing the interior of a wind turbine blade extending along a longitudinal axis from a root end to a tip end, the wind turbine blade comprising a blade shell forming a profiled contour including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending therebetween, wherein the profiled contour is divided into a root region having a substantially circular or elliptical profile closest to the root end with a root diameter being the chord length at the root end, an airfoil region having a lift-generating profile furthest away from the root end, and a transition region between the root region and the airfoil region, the transition region having a profile gradually changing in the radial direction from the circular or elliptical profile of the root region to the lift-generating profile of the airfoil region, the wind turbine blade further comprises opposing spar caps and one or more shear webs extending along the longitudinal axis, the method comprising the steps of: providing the wind turbine blade; from the exterior of the wind turbine blade, removing one or more blade shell portions of the blade shell in the airfoil region of the blade shell of the wind turbine blade at a chordwise distance from the opposing spar caps so as to establish one or more respective temporary access windows for an operator to the interior of the wind turbine blade; performing a task within the interior of the wind turbine blade via the one or more temporary access windows; from the exterior of the wind turbine blade, inserting one or more precured plug components in the one or more temporary access windows, respectively; and irreversibly securing the one or more precured plug components to the blade shell so as to close the one or more temporary access windows. The technical advantage of this method is that it allows for efficient interior access and task performance within the wind turbine blade while minimizing damage to the structural integrity and reducing labour and material costs compared to traditional methods. P2612PC00 (701356-WO-l)

[0016] 3

[0017] Additionally or alternatively, the step of removing the one or more blade shell portions may be performed by any suitable means. Suitable means may include mechanical cutting, laser cutting, waterjet cutting, or grinding. The technical advantage is providing flexibility and precision in the method of removal, adapting to various conditions and reducing the risk of damage during access window creation.

[0018] Additionally or alternatively, the chordwise distance may be at least 100 mm. The chordwise distance may be preferably at least 150 mm. More preferably, the chordwise distance may be at least 200 mm. Most preferably, the chordwise distance may be at least 300 mm. The technical advantage is ensuring adequate spacing from structural elements, enhancing the safety and structural integrity during maintenance or retrofitting operations.

[0019] Additionally or alternatively, the method may be performed up-tower. The technical advantage is enabling the maintenance or modification of the wind turbine blade while it remains mounted, thus reducing downtime and potentially lowering costs associated with dismantling and reassembly. In the context of the present disclosure, performing a method up-tower is understood as performing the method while the wind turbine blade is mounted on a hub of a wind turbine.

[0020] Additionally or alternatively, the respective one or more temporary access windows may comprise one or more lips extending at least partly around a perimeter of the respective one or more temporary access windows. The step of inserting one or more precured plug components in the one or more temporary access windows, respectively, may include resting the one or more precured plug components on the respective one or more lips of the one or more access windows. The technical advantage is providing a stable resting surface for the plug components, enhancing the ease of installation and improving the seal integrity.

[0021] Additionally or alternatively, the one or more lips may extend at least 5 mm. Preferably, the one or more lips may extend at least 10 mm. More preferably, the one or more lips may extend at least 20 mm from a perimeter of the respective one or more temporary access windows at the exterior surface of the blade shell towards a center of the respective one or more temporary access windows. The technical advantage is ensuring sufficient overlap for secure plug placement, enhancing the structural stability of the repair.

[0022] Additionally or alternatively, the one or more temporary access windows may comprise a first temporary access window having a first shape, and a second temporary access window having a second shape different from the first shape. The technical advantage is providing flexibility in access window design to accommodate different maintenance requirements or internal configurations. P2612PC00 (701356-WO-l)

[0023] 4

[0024] Additionally or alternatively, the first shape may comprise a first length along the spanwise direction, and the second shape may comprise a second length along the spanwise direction being different from the first length. The technical advantage is tailoring access windows to specific repair or modification needs, optimizing access while preserving blade integrity.

[0025] Additionally or alternatively, the first shape may be substantially circular, and the second shape may be elongated compared to the first shape. Preferably, the second shape may comprise a straight section and two opposite rounded end sections. The technical advantage is offering design versatility to match the specific access and repair needs, enhancing the method's adaptability.

[0026] Additionally or alternatively, the one or more blade shell portions may be undamaged prior to removal thereof. The technical advantage is conserving the integrity of the blade structure, facilitating the repair process without introducing additional damage.

[0027] Additionally or alternatively, the step of removing the one or more blade shell portions may include discarding the one or more removed blade shell portions. The technical advantage is simplifying the repair process by eliminating the need to preserve removed sections for reuse, thereby reducing complexity and potential errors.

[0028] Additionally or alternatively, the airfoil section of the wind turbine blade may be continuous. The technical advantage is maintaining aerodynamic efficiency and structural coherence, crucial for optimal blade performance. In the context of the present disclosure, a continuous airfoil section of a wind turbine blade may also refer to a non-jointed wind turbine blade (in contrast to segmented wind turbine blades joined by a joint) or otherwise integral wind turbine blade. However, the wind turbine blade may also be a segmented or jointed wind turbine blade. In such embodiments, the temporary access windows established according to the present disclosure are distinct from any access windows used to form or inspect the joint (e.g. pin joint) between blade segments. The temporary access windows of the present disclosure are typically configured to be established only once to perform a one-off servicing or maintenance task, while access windows associated with the segment joint are often used to periodically inspect and maintain the joint and thus are openable and closable on demand.

[0029] Additionally or alternatively, the method may be performed after completion of manufacturing of the provided wind turbine blade. The technical advantage is allowing for post-manufacturing enhancements or repairs, extending the service life and functionality of the wind turbine blade.

[0030] Additionally or alternatively, the step of performing a task within the interior of the wind turbine blade via the one or more temporary access windows may include performing one or more of: P2612PC00 (701356-WO-l)

[0031] 5

[0032] Preferably performing a method according to a second aspect of the present disclosure described below; retrofitting one or more functional components, such as electrical components, e.g., lightning protection components, sensor components, and heating elements, in the interior of the wind turbine blade; and performing structural repairs, such as bond line repairs, delamination repairs, and crack repairs in the interior of the wind turbine blade.

[0033] The technical advantage is enhancing the operational capabilities and longevity of the wind turbine blade through a wide range of possible internal interventions. Advantageously, the task performed is a method according to the second aspect as the establishment of temporary access windows provides an efficient way of inserting fibre-reinforced plates as described in the method according to the second aspect into the interior of the wind turbine blade.

[0034] Additionally or alternatively, the step of irreversibly securing the one or more precured plug components to the blade shell may comprise applying a second adhesive to, for example a circumference of, the one or more precured plug components, and curing the second adhesive so as to irreversibly secure the one or more precured plug components to the blade shell so as to close the one or more temporary access windows, respectively. The technical advantage is ensuring a robust and durable seal that maintains structural integrity and prevents ingress of external elements.

[0035] Additionally or alternatively, the one or more plug components may be a composite material. Preferably, the composite material may be a composite sandwich material, such as one or more fibre layers on each side of a core material. The fibre layers may be glass fibre layers, carbon fibre layers or a hybrid fibre layer material. Preferably, the type of fibres (i.e., glass, carbon or hybrid) may be the same as fibres of the blade shell adjacent to the one or more temporary access windows. The core material may be a foamed polymer or balsa wood. Preferably, the core material is the same as a core material of the blade shell adjacent to the one or more temporary access windows. The technical advantage is providing a lightweight yet strong solution that matches the mechanical properties of the blade shell, thereby optimizing the repair's effectiveness.

[0036] Additionally or alternatively, the method may further comprise the steps of: recessing, for example, by grinding, a circumferential portion of the exterior surface of the blade shell at least partly, preferably entirely, around the one or more access windows; and P2612PC00 (701356-WO-l)

[0037] 6 overlaminating one or more layers, such as fibre-reinforced layers, over the respective one or more precured plug components so that the one or more overlaminated layers may be arranged in the recessed portion and substantially flush with the exterior surface of the blade shell.

[0038] The technical advantage is providing enhanced reinforcement and aerodynamic efficiency by ensuring the repair is seamlessly integrated with the blade's surface.

[0039] A second aspect of the present disclosure relates to a method of repairing a wind turbine blade extending along a longitudinal axis from a root end to a tip end, the wind turbine blade comprising a blade shell forming a profiled contour including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending therebetween, wherein the profiled contour is divided into a root region having a substantially circular or elliptical profile closest to the root end with a root diameter being the chord length at the root end, an airfoil region having a lift-generating profile furthest away from the root end, and a transition region between the root region and the airfoil region, the transition region having a profile gradually changing in the radial direction from the circular or elliptical profile of the root region to the liftgenerating profile of the airfoil region, the wind turbine blade further comprises opposing spar caps and one or more shear webs extending along the longitudinal axis, the method comprising the steps of: providing the wind turbine blade, wherein the one or more shear webs includes a first shear web having a damaged portion, and wherein the blade shell of the wind turbine blade comprises one or more access windows providing access to the damaged portion from the exterior of the wind turbine blade; providing one or more fibre-reinforced plates; at the damaged portion, identifying a target area for reinforcement on a side surface of the first shear web; inserting the one or more fibre- reinforced plates having a first adhesive on a first side thereof through the one or more access windows;

[0040] - applying the first side of the one or more fibre-reinforced plates to the target area of the first shear web; and causing or allowing the first adhesive to cure so as to secure the one or more fibre-reinforced plates thereby reinforcing the damaged portion of the first shear web. P2612PC00 (701356-WO-l)

[0041] 7

[0042] The technical advantage is providing a targeted repair solution that restores the shear web's structural integrity without extensive disassembly or compromise to the surrounding structures, thus reducing downtime and enhancing repair efficacy.

[0043] In the context of the present disclosure, a damaged portion is understood as a portion of a component with unintended damage and is referred before any corrective action has been taken. Thus, a component which has had a portion intentionally removed, e.g. by grinding out a damaged portion, is no longer understood as having a damaged portion but rather as a portion undergoing repair. The damage may refer to any unintended damage within the laminate of the component including, but not limited to, cracks, delamination, fibre misalignment, chipped or holes. However, the method is preferably applied to repair a damaged portion of shear web caused by surface cracks in the laminate or subsurface cracks within the laminate that are, for example, caused during transportation of the wind turbine blade from the blade manufacturing facility to the erection site of the associated wind turbine.

[0044] Additionally or alternatively, the one or more shear webs may comprise a second shear web, and the first shear web may be arranged towards the trailing edge of the wind turbine blade, and the second shear web may be arranged towards the leading edge of the wind turbine blade. The technical advantage is enhancing the versatility and comprehensiveness of the repair approach, accommodating complex internal configurations.

[0045] Additionally or alternatively, the one or more fibre-reinforced plates respectively may comprise one or more first fibre layers embedded in a first resin. The technical advantage is ensuring compatibility with existing blade materials, leading to a more cohesive and effective repair.

[0046] Additionally or alternatively, the one or more first fibre layers may comprise a bottom first fibre layer, a top first fibre layer, and one or more intermediate first fibre layers arranged between the bottom fibre layer and the top fibre layer. The extent of the first fibre layers may taper from the bottom first fibre layer to the top first fibre layer. The technical advantage is optimizing load distribution and minimizing stress concentrations, improving the durability of the repair.

[0047] Additionally or alternatively, the bottom first fibre layer may have the largest extent, and each subsequent first fibre layer towards the top first fibre layer may have a smaller extent than the previous first fibre layer so that the first fibre layers may substantially form a pyramid shape. The technical advantage is enhancing the strength and stability of the repair by mimicking natural load paths and reducing abrupt transitions. P2612PC00 (701356-WO-l)

[0048] 8

[0049] Additionally or alternatively, the first adhesive may be different from the first resin of the one or more fibre-reinforced plates. The technical advantage is allowing for the selection of adhesives tailored to specific bonding needs, further ensuring the longevity and effectiveness of the repair.

[0050] Additionally or alternatively, the one or more first fibre layers may be of the same fibre material as the first shear web. The technical advantage is ensuring material compatibility, which is crucial for structural integrity and performance consistency.

[0051] Additionally or alternatively, the one or more fibre-reinforced plates may be precured, e.g. the resin may be cured when the one or more fibre-reinforced plates are provided. Alternatively, the one or more fibre-reinforced plates may be preimpregnated. The technical advantage is simplifying the installation process and reducing cure times, thereby expediting the repair process.

[0052] Additionally or alternatively, the target area may exceed or overlap the damaged portion by a predetermined length and / or predetermined height. This predetermined length may be preferably at least 15 mm, more preferably at least 30 mm, and even more preferably at least 50 mm along the longitudinal axis and / or preferably at least 15 mm, preferably at least 30 mm, and more preferably at least 50 mm along a thickness direction extending between the opposing spar caps. The target area may overlap the damaged portion on both sides along the longitudinal axis and / or the thickness direction by the predetermined length. The technical advantage is ensuring comprehensive coverage and reinforcement, mitigating the risk of further damage.

[0053] Additionally or alternatively, the method may further comprise cleaning of the target area in preparation for adhesion of the one or more fibre-reinforced plates. The technical advantage is enhancing adhesive performance and ensuring a strong bond between the fibre-reinforced plate(s) and the shear web.

[0054] Additionally or alternatively, the step of identifying a target area for reinforcement may further comprise the steps of: measuring the flatness of the target area; and in accordance with a determination that the flatness of the target area exceeds a predetermined threshold, preparing, such as grinding, etc., the side surface of the first shear web at the target area until the flatness of the target area is within the predetermined threshold.

[0055] The technical advantage is ensuring optimal contact and adhesion, thus enhancing the effectiveness and durability of the repair. The predetermined threshold is selected and the flatness is measured using the appropriate technical standard as is well known to the skilled person. P2612PC00 (701356-WO-l)

[0056] 9

[0057] Additionally or alternatively, the method may further include in accordance with a determination that the flatness of the target area is within a predetermined threshold, forgoing preparation of the side surface of the first shear web at the target area. The technical advantage is reducing unnecessary labour and material use, streamlining the repair process.

[0058] Additionally or alternatively, the step of applying the first side of the one or more fibre-reinforced plates to the target area of the first shear web may comprise pressing the first side of the one or more fibre-reinforced plates to the target area of the first shear web using one or more pressure tools so as to apply at least a predetermined pressure for at least a predetermined time period. The technical advantage is ensuring consistent application of pressure, which aids in achieving a durable adhesive bond.

[0059] Additionally or alternatively, the method may further comprise attaching the one or more pressure tools to the blade shell at the one or more access windows, and urging a portion of the one or more pressure tools onto the respective one or more fibre-reinforced plates. The technical advantage is facilitating precise application of pressure, ensuring a high-quality bond and effective repair.

[0060] Additionally or alternatively, the method may further comprise the steps of: providing one or more first fibre-reinforced plates having a first length, and one or more second fibre-reinforced plates having a second predetermined length greater than the first predetermined length; in accordance with a determination that the target area has a length, e.g., along the longitudinal axis, less than or equal to the first predetermined length, selecting a first fibre-reinforced plate for application to the target area; in accordance with a determination that the target area has a length, e.g., along the longitudinal axis, that is greater than the first predetermined length and that is equal to or less than the second predetermined length, selecting a second fibre-reinforced plate for application to the target area; and in accordance with a determination that the length of the target area is greater than the second predetermined length, selecting a combination of one or more first fibre-reinforced plates and / or one or more second fibre-reinforced plates for application to the target area so that the summed length of the selected reinforced plates is equal to or greater than the length of the target area.

[0061] The technical advantage is providing a modular approach to repair, allowing for customization based on the specific damage and ensuring efficient use of materials. P2612PC00 (701356-WO-l)

[0062] 10

[0063] A third aspect of the present disclosure relates to a repaired wind turbine blade obtainable by a method according to any one of the previous claims. The technical advantage is providing a wind turbine blade that has undergone methodical repair or modification, ensuring enhanced performance and longevity.

[0064] A fourth aspect of the present disclosure relates to a repaired wind turbine blade extending along a longitudinal axis from a root end to a tip end, the wind turbine blade comprising a blade shell forming a profiled contour including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending therebetween, wherein the profiled contour is divided into a root region having a substantially circular or elliptical profile closest to the root end with a root diameter being the chord length at the root end, an airfoil region having a liftgenerating profile furthest away from the root end, and a transition region between the root region and the airfoil region, the transition region having a profile gradually changing in the radial direction from the circular or elliptical profile of the root region to the lift-generating profile of the airfoil region, the wind turbine blade further comprises opposing spar caps and one or more shear webs extending along the longitudinal axis, wherein the one or more shear webs comprises a suction-side web flange attached to a suction-side spar cap, a pressure-side web flange attached to a pressureside spar cap, and a web panel extending between the suction-side web flange and the pressureside web flange, wherein the web panel of a first shear web of the one or more shear webs comprises a damaged portion, and wherein the first shear web comprises one or more fibre-reinforced plates adhered to a side surface of the web panel overlapping the damaged portion, preferably so as to reinforce the web panel overlapping the damaged portion. The technical advantage is providing a wind turbine blade that has been structurally reinforced to address damage, enhancing its durability and operational efficiency.

[0065] A fifth aspect of the present disclosure relates to a kit of parts for repairing a wind turbine blade by a method according to any one of the first aspect or the second aspect, comprising:

[0066] - one or more fibre-reinforced plates configured for reinforcing a damaged portion of a first shear web of the wind turbine blade; and

[0067] - one or more precured plug components configured for closing one or more respective temporary access windows of the wind turbine blade.

[0068] The technical advantage is offering a comprehensive solution for wind turbine blade repair, facilitating efficient and effective maintenance and modifications. P2612PC00 (701356-WO-l)

[0069] 11

[0070] Additionally or alternatively, the kit of parts may comprise a first adhesive configured for adhering the one or more fibre-reinforced plates to the first shear web of the wind turbine blade. The technical advantage is ensuring a strong bond between repair components, crucial for the repair's durability and effectiveness.

[0071] Additionally or alternatively, the kit of parts may comprise one or more pressure tools configured for pressing the one or more fibre-reinforced plates to the first shear web during curing of the first adhesive. The technical advantage is providing the necessary pressure to ensure proper adhesive curing, enhancing the repair quality.

[0072] Additionally or alternatively, the kit of parts may comprise a second adhesive configured for irreversibly securing the one or more precured plug components in the respective one or more temporary access windows. The technical advantage is enabling a secure and permanent closure of access windows, preserving the blade's structural integrity.

[0073] BRIEF DESCRIPTION OF THE FIGURES

[0074] Embodiments of the disclosure will be described in more detail in the following with regard to the accompanying figures. The figures show one way of implementing the present disclosure and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

[0075] Figure 1 is a schematic perspective view of a wind turbine illustrating the main components including the tower, nacelle, hub, and blades.

[0076] Figure 2 is a schematic perspective view of a wind turbine blade for a wind turbine as shown in Fig. 1 detailing the various regions from the root to the tip.

[0077] Figure 3A is a schematic cross-sectional view of the wind turbine blade showing the internal beam structure including spar caps and shear webs.

[0078] Figure 3B is a schematic cross-sectional view of an alternative configuration of the internal beam structure with a box spar structure.

[0079] Figure 4 is a schematic perspective view of a section of an airfoil region of the wind turbine blade having two temporary access windows and indicating cross-sectional line A-A.

[0080] Figure 5A is a schematic cross-sectional view along the cross-sectional line A-A of Figure 4 illustrating a temporary access window in the wind turbine blade having a damaged shear web. P2612PC00 (701356-WO-l)

[0081] 12

[0082] Figure 5B is a schematic cross-sectional view along the cross-sectional line A-A of Figure 4 showing the introduction of a fibre-reinforced plate through the temporary access window.

[0083] Figure 6A is a schematic cross-sectional view along the cross-sectional line A-A of Figure 4 showing the fibre-reinforced plate attached to damaged shear web.

[0084] Figure 6B is a schematic cross-sectional view along the cross-sectional line A-A of Figure 4 showing the process of introducing the precured plug component in the temporary access window.

[0085] Figure 7A is a schematic cross-sectional view along the cross-sectional line A-A of Figure 4 showing the precured plug component being irreversibly secured and closing the temporary access window.

[0086] Figure 7B is a schematic cross-sectional view at detail view B shown in Figure 7A of the joint between the precured plug component and the blade shell.

[0087] Figure 8A is a schematic side-view of a shear web comprising a damaged portion.

[0088] Figures 8B-8C and 8D-8E are schematic views of a first fibre-reinforced plate and a second fibre- reinforced plate, respectively.

[0089] DETAILED DESCRIPTION

[0090] Various exemplary embodiments and details are described hereinafter, with reference to the figures when relevant. It should be noted that the figures may or may not be drawn to scale and that elements of similar structures or functions are represented by like reference numerals throughout the figures. It should also be noted that the figures are only intended to facilitate the description of the embodiments. They are not intended as an exhaustive description of the invention or as a limitation on the scope of the invention. In addition, an illustrated embodiment needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced in any other embodiments even if not so illustrated, or if not so explicitly described.

[0091] Fig. 1 illustrates a conventional modern upwind wind turbine 2 according to the so-called "Danish concept" with a tower 4, a nacelle 6 and a rotor with a substantially horizontal rotor shaft which may include a tilt angle of a few degrees. The rotor includes a hub 8 and three blades 10 extending radially from the hub 8, each having a blade root 16 nearest the hub and a blade tip 14 furthest from the hub 8.

[0092] Fig. 2 shows a schematic view of an exemplary wind turbine blade 10. The wind turbine blade 10 has the shape of a conventional wind turbine blade with a root end 17 and a tip end 15 and comprises P2612PC00 (701356-WO-l)

[0093] 13 a root region 30 closest to the hub, a transition region 32, an airfoil region 34, and a tip region 36 situated at the tip end 15 of the wind turbine blade 10. The blade 10 comprises a leading edge 18 facing the direction of rotation of the blade 10, when the blade is mounted on the hub 8, and a trailing edge 20 facing the opposite direction of the leading edge 18.

[0094] The airfoil region 34 (also called the profiled region) has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region 30 due to structural considerations has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade 10 to the hub. The diameter (or the chord) of the root region 30 may be constant along the entire root region 30. The transition region 32 has a transitional profile gradually changing from the circular or elliptical shape of the root region 30 to the airfoil profile of the airfoil region 34. The chord length of the transition region 32 typically increases with increasing distance r from the hub. The airfoil region 34 has an airfoil profile with a chord extending between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing distance r from the hub. A shoulder 38 of the blade 10 is defined as the position where the blade 10 has its largest chord length. The shoulder 38 is typically provided at the boundary between the transition region 32 and the airfoil region 34.

[0095] It should be noted that the chords of different sections of the blade normally do not lie in a common plane, since the blade may be twisted and / or curved (i.e. pre-bent), thus providing the chord plane with a correspondingly twisted and / or curved course, this being most often the case in order to compensate for the local velocity of the blade being dependent on the radius from the hub.

[0096] The wind turbine blade 10 is, in this example, formed as a segmented or jointed blade as shown in Figure 2. The wind turbine blade 10 is separated in a root segment 21 and a tip segment 22 connected by a chordwise joint 23. The chordwise joint 26 is typically formed as a pin joint, wherein one of the root and tip segment 21, 22 comprises a receiving section and the other one of the root and tip segment 21, 22 comprises an insertion section configured for insertion into the receiving section and for being locked with a pin.

[0097] The wind turbine blade 10 further comprises two temporary access windows 50, 50' located in the airfoil region 34 of the pressure side shell part 24 and towards the trailing edge 20. The temporary access windows 50, 50' are also distanced from the chordwise joint 23 and is made for a different purpose than forming this chordwise joint 23. Accordingly, the wind turbine blade 10 may in other embodiments have a continuous airfoil region 34 and tip region 36, and thus be non-segmented or non-jointed.

[0098] The wind turbine blade 10 generally includes a shell 13 that may be formed in a one-shot process or comprise a pressure side shell part 24 and a suction side shell part 26 each moulded in a dedicated P2612PC00 (701356-WO-l)

[0099] 14 shell mould and typically formed using a resin infusion process, such as vacuum assisted resin transfer infusion moulding (VARTM). After moulding the pressure side shell part 24 and suction side shell part 26, these are bonded together at a bond line extending along the leading edge 18 and trailing edge 20 of the wind turbine blade 10 to form a continuous exterior blade surface U defining the aerodynamic profile of the wind turbine blade 10. The shell 13 is relatively lightweight often comprising no more than a few shell layers of typically glass fibres with an exterior gel coat. Thus, the shell 13 has structural properties (e.g., stiffness, buckling resistance and strength) which are not configured to withstand the bending moments and other loads exerted on the wind turbine blade but is primarily configured to maintain the airfoil profile during operation.

[0100] The transfer of flapwise and edgewise loads experienced by the wind turbine blade 10 to the hub 8 is primarily performed by one or more beam structures 40 of the wind turbine blade 10. Such a beam structure 40 comprises opposing spar caps 41, 42 with one or more shear webs 43, 43' connecting the opposing spar caps 41, 42 as shown in Figures 3A and 3B. The spar caps 41, 42 are configured to absorb the flapwise and edgewise loads of the wind turbine blade 10 and are thus formed from a fibre-reinforced composite material, such as layered fibre sheets or one or more pultrusions. The spar caps 41, 42 are often much thicker than shell layers of the shell 13. For example, the thickness of the spar caps 41, 42 along the thickness direction T may be an order of magnitude greater than the thickness of the shell 13. The one or more shear webs 43, 43' are configured to absorb shear forces and are typically formed from a web panel 46, 46' of a fibre- reinforced composite, for example a sandwich construction comprising a core material sandwiched between layers of fibre material.

[0101] Generally, the spar caps 41, 42 of the beam structure 40 are integrated into or embedded within the shell 13 (e.g. within the respective suction and pressure side shell parts 24, 26), and the one or more shear webs 43, 43' is manufactured separately and subsequently adhered to interior surfaces of or adjacent to the integrated spar caps 41, 42, for example via web flanges 44, 44', 45, 45'. Such an arrangement is shown in Figure 3A, which may also be referred to as a load-carrying shell, showing a first shear web 43 with a first web panel 46 between a first suction side web flange 44 and a first pressure side web flange 45 as well as a second shear web 43' with a second web panel 46' between a second suction side web flange 44' and a second pressure side web flange 45'. Alternatively, the beam structure 40 can be manufactured separately from the shell 13 or shell parts 24, 26. The separately manufactured beam structure 40 can then subsequently adhered to interior surfaces of the shell 13. In such an arrangement, the beam structure 40 may be a separately made box spar as shown in Figure 3B.

[0102] Figure 4 provides a detailed representation of a section of the airfoil region 34 of the wind turbine blade 10 of Figure 2, illustrating the interface between the blade shell 13 and beam structure 40 P2612PC00 (701356-WO-l)

[0103] 15 with the spar caps 41 and 42 integrated into the blade shell 13. In contrast to Figure 3A, the beam structure 40 of this embodiment comprises a single shear web 43. Otherwise, the construction is similar or even the same. As seen, Figure 4 shows the provision of a first access window 50 and a second access window 50' at a chordwise distance 58 of at least 100 mm from the pressure side spar cap 41. The access windows 50, 50' are provided by any suitable means, e.g. laser cutting, waterjet cutting, grinding, etc., but are preferably provided by mechanical cutting. As the method is applied to establish a temporary access for performing an interior task as will be described below, the removed blade shell sections were undamaged prior to providing the access windows 50, 50' and can be discarded after removal. The access windows 50, 50' can be established up-tower, i.e. while the wind turbine blade 10 is mounted to the hub 8 as shown in Figure 1. The first access window 50 has a first shape of a first length 50L along the longitudinal axis L, e.g. an elongated shape with a straight midsection and two circularly curving end sections on opposite sides of the midsection. A perimeter 52 around the first access window 50 is thus continuous without any kinks providing smooth load paths around the access windows. The same applies to the perimeter 52'of the second access window 50'. This reduces the access window's impact on shell stiffness. A stiffness analysis, such as a finite element analysis, may be performed to validate that the stiffness reduction is insignificant. Accordingly, the shape of the first access window 50 allows for the insertion of a fibre-reinforced plate 60 therethrough as shown in Figure 5B. Returning to Figure 4, the second access window 50' has a second perimeter 52' defining a second shape with a second length 50L' along the longitudinal axis L. The second length 50L' is shorter than the first length 50L. The second shape is circular or elliptical and is configured for allowing an operator to insert a hand therethrough to assist during insertion of the fibre-reinforced plate through the first access window 50 and to allow pressure to be applied to the fibre-reinforced plate during adhesive curing. However, if the fibre-reinforced plate is relatively short, the second access window 50' may not be required and thus be omitted.

[0104] Figure 3A and Figure 4 further indicate the longitudinal axis L as well as the thickness direction T and the chordwise direction C of the wind turbine blade, which are not reiterated in the description of the other figures but apply consistently to the other figures.

[0105] Figures 5A, 5B, 6A, 6B, 7A, 7B illustrate the placement and features of the first temporary access window 50 along cross-sectional line A-A of Figure 4. As shown in these figures, the web panel 46 of the first shear web 43 comprises a damaged portion 48 requiring reinforcement to avoid further damaging the shear web. The damaged portion 48 may for instance be a stiffness irregularity of the web panel 46, for example a surface crack or subsurface crack. The figures illustrate a method according to the present disclosure of reinforcing the damaged portion 48. As the features of the P2612PC00 (701356-WO-l)

[0106] 16 first temporary access window 50 apply equally to the second access window 50', a similar description of the second access window 50' has been omitted to avoid reiteration.

[0107] Returning to Figure 5A, the first access window 50 is positioned in the airfoil region of the blade to allow for interior access without compromising the blade's structural integrity. The first access window 50 comprises a first perimeter 52 and a first lip 53, providing a stable-resting surface for the precured plug component 70 shown in Figure 7A. The blade shell 15 comprises a first recessed circumferential portion 54 surrounding the first access window 50. As also described for Figure 4, the first access window 50 is positioned at a chordwise distance 58 from the spar caps 41, 42. In this example, the first access window 50 is placed on the suction side, and thus the chordwise distance 58 is from the suction side spar cap 41, but the access window(s) can also be placed on the pressure side of the wind turbine blade. Once the access window(s) is / are established, a target area 80 on the side surface 47 of the web panel 46 of the first shear web 43 can be identified for the intended reinforcement. This is described in greater details below in connection with Figure 8A.

[0108] Turning to Figure 5B, the fibre-reinforced plate 60 is inserted through the first access window 50. Prior to insertion, a first adhesive 64 has been applied to a side of the fibre-reinforced plate 60. The operator may, in addition to via the first access window 50, also handle the fibre-reinforced plate 60 via the second access window 50' during the insertion and while placing the fibre-reinforced plate 60 on the target area 80 in the interior of the wind turbine blade.

[0109] As shown in Figure 6A, the fibre-reinforced plate 60 is placed on the target area 80 so that the first adhesive 64 contacts the side surface 47 of the web panel 46 of the first shear web, and the fibre- reinforced plate 60 overlaps the damaged portion 48. A pressure tool 90 is attached to the wind turbine blade, e.g. to the blade shell 15 at the access window as shown, and applies pressure to the surface of the fibre-reinforced plate 60 opposite of the first adhesive 64 so as to ensure a good adhesion between the fibre-reinforced plate 60 and the web panel 46. Even though the shear web 43 still comprises the damaged portion 48, once the first adhesive 64 is sufficiently cured, the first shear web 43 is reinforced and thus increases the expected lifetime, e.g. the fatigue reserve, of the beam structure 40. Thus, the access window(s) can now be closed. Although the above method involves the reinforcement of the first shear web 43, other types of reinforcement, repairs, service, retrofitting or maintenance tasks can be performed with the present method of establishing temporary access window(s).

[0110] Turning to Figures 6B and 7A, the process of closing the access window(s) is described. As shown in Figure 6B, a first precured plug component 70 is provided and brought towards the first access window 50. As shown in Figure 7A, the first precured plug component 70 is placed in the first access window 50 resting on the lip 53 thereof. The first precured plug component 70 is sized to match the P2612PC00 (701356-WO-l)

[0111] 17 first shape of the first access window 50 with tight tolerances, and thus allows an excellent fit where the gap left between the first precured plug component 70 and the perimeter 52 of the first access window can be provided within a predetermined tolerance range ensuring a good adhesion and reestablishment of the exterior surface U at the first access window 50.

[0112] Figure 7B shows a more detailed view of the cross-section shown in Figure 7A at detail view B. As seen, the gap between the first precured plug component 70 and the perimeter 52 of the first access window 50 is filled with a second adhesive 74. In this embodiment, the lip 53 extends at least 20 mm from the perimeter 52 of the first temporary access window 50 at the exterior surface U of the blade shell 15 towards a centre of the first temporary access window 50, but this distance may vary in other embodiments depending on the required overlap between the lip 53 and the precured plug component 70. Once the precured plug component 70 has been placed and adhered in the first access window 50, one or more fibre layers 55 are overlaminated over the first precured plug component 70 so that the one or more overlaminated layers 55 are arranged in the recessed circumferential portion 54 and substantially flush with the exterior surface U of the blade shell 15. As shown, the recessed circumferential portion may comprise at least two levels, and at least one overlaminated fibre layer may be arranged in each level. The at least two levels may include an inner level and an outer level, wherein the outer level overlaps and extends beyond the inner level.

[0113] Figure 8A shows a schematic side view of the first shear web 43 indicating the length 48L of the damaged portion 48 along the longitudinal axis L of the wind turbine blade 10 and the height 48T in the thickness direction T of the wind turbine blade 10. As shown, the target area 80 for reinforcement exceeds, e.g. symmetrically, beyond the extent of the damaged portion both along the longitudinal axis L and in the thickness direction T. In this example, the target area 80 exceeds or overlaps both sides of the damaged portion 48 by a predetermined length of at least 15 mm along the longitudinal axis L and both sides of the damaged portion 48 by a predetermined height of at least 15 mm along a thickness direction T.

[0114] Figure 8B and 8C show schematic views of a first fibre-reinforced plate 60, which is elongated and has a first length 60L intended to be arranged along the longitudinal axis L of the wind turbine blade. As shown, the first fibre-reinforced plate 60 comprises a bottom first fibre layer 61, a top first fibre layer 63, and two intermediate first fibre layers 62 arranged between the bottom fibre layer 61 and the top fibre layer 63. The extent of the first fibre layers tapers from the bottom first fibre layer 61 to the top first fibre layer 63. Further, the bottom first fibre layer 61 has the largest, e.g. areal, extent, and each subsequent first fibre layer 62, 63 towards the top first fibre layer 63 has a smaller, e.g. areal, extent than the previous first fibre layer so that the first fibre layers 61, 62, 63 substantially form a pyramid shape. The same applies to the second fibre-reinforced plate 60' shown below. P2612PC00 (701356-WO-l)

[0115] 18

[0116] Figure 8D and 8E show schematic views of a second fibre-reinforced plate 60' which is elongated and has a second length 60L' intended to be arranged along the longitudinal axis L of the wind turbine blade. As shown, the second length 60L' is longer than the first length 60. The second length 60L' may be predetermined as the longest length that can feasibly be inserted into through the first access window 50'. The fibre-reinforced plates 60, 60' are precured, e.g. a precured laminate of precured fibre layers and / or pultrusions, in a preferred embodiment, but may in others comprise preimpregnated fibre sheets that are cured after placement of the fibre-reinforced plates 60, 60' on the shear web 63.

[0117] Depending on the length 80L and height 80T of the target area 80 as shown in Figure 8A, it can be determined which of the fibre-reinforced plates to use. In this case, the length 80L of the target area 80 exceeds the first length 60L but is less than the second length 60L'. Therefore, the second fibre- reinforced plate 80' is selected for use as reinforcement of the damaged portion 48. This is advantageous when the exact extent of the damaged portion is not known prior to establishing the access windows, and time efficiency is important as technicians can quickly determine the extent of damage and select the appropriate fibre-reinforced plate. Furthermore, if the extent of the damage is larger than the second length, a combination of one or more first fibre-reinforced plates 60 and one or more second fibre-reinforced plates 60' can be used together with the establishment of additional access windows 50, 50' as appropriate. Thus, by providing fibre-reinforced plates 60, 60' of predetermined modular lengths and precured plug components 70, 70' sized to fit respective access windows 50, 50', a modular kit of parts can be provided for efficiently establishing access, providing shear web repairs, and closing the access windows with reduced or minimal impact on shell stiffness.

[0118] Throughout the description, the use of the terms "first", "second", "third", "fourth", "primary", "secondary", "tertiary" etc. does not imply any particular order or importance, but are included to identify individual elements. Furthermore, the labelling of a first element does not imply the presence of a second element and vice versa.

[0119] LIST OF ITEMS

[0120] The following is a list of items representing embodiments of the present disclosure.

[0121] 1. A method of accessing the interior of a wind turbine blade extending along a longitudinal axis from a root end to a tip end, the wind turbine blade comprising a blade shell forming a profiled contour including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending therebetween, wherein the profiled contour is divided into a root region having a substantially circular or elliptical profile closest to the root end with a root diameter being the chord length at the root end, an airfoil region having a lift-generating profile P2612PC00 (701356-WO-l)

[0122] 19 furthest away from the root end, and a transition region between the root region and the airfoil region, the transition region having a profile gradually changing in the radial direction from the circular or elliptical profile of the root region to the lift-generating profile of the airfoil region, the wind turbine blade further comprises opposing spar caps and one or more shear webs extending along the longitudinal axis, the method comprising the steps of: providing the wind turbine blade;

[0123] - from the exterior of the wind turbine blade, removing one or more blade shell portions of the blade shell in the airfoil region of the blade shell of the wind turbine blade at a chordwise distance from the opposing spar caps so as to establish one or more respective temporary access windows for an operator to the interior of the wind turbine blade; performing a task within the interior of the wind turbine blade via the one or more temporary access windows;

[0124] - from the exterior of the wind turbine blade, inserting one or more precured plug components in the one or more temporary access windows, respectively; and

[0125] - irreversibly securing the one or more precured plug components to the blade shell so as to close the one or more temporary access windows.

[0126] 2. A method according to item 1, wherein the step of removing the one or more blade shell portions is performed by any suitable means, preferably mechanical cutting, laser cutting, waterjet cutting, grinding, etc.

[0127] 3. A method according to any one of the previous items, wherein the chordwise distance is at least 100 mm, preferably at least 150 mm, more preferably at least 200 mm, most preferably at least 300 mm.

[0128] 4. A method according to any one of the previous items, wherein the method is performed up- tower.

[0129] 5. A method according to any one of the previous items, wherein the respective one or more temporary access windows comprises one or more lips extending at least partly, preferably entirely, around a perimeter of the respective one or more temporary access windows, and wherein the step of inserting one or more precured plug components in the one or more temporary access windows, respectively, includes resting the one or more precured plug components on the respective one or more lips of the one or more access windows. P2612PC00 (701356-WO-l)

[0130] 20

[0131] 6. A method according to item 5, wherein the one or more lips extends at least 5 mm, preferably at least 10 mm, and more preferably at least 20 mm, from the perimeter of the respective one or more temporary access windows at the exterior surface of the blade shell towards a centre of the respective one or more temporary access windows.

[0132] 7. A method according to any one of the previous items, wherein the one or more temporary access windows comprises a first temporary access window having a first shape, and a second temporary access window having a second shape different from the first shape.

[0133] 8. A method according to item 7, wherein the first shape comprises a first length along the spanwise direction, and the second shape comprises a second length along the spanwise direction being different from the first length.

[0134] 9. A method according to any one of items 7-8, wherein the first shape is substantially circular, and the second shape is elongated compared to the first shape, preferably the second shape comprises a straight section and two opposite rounded, e.g. circularly curving, end sections.

[0135] 10. A method according to any one of the previous items, wherein the one or more blade shell portions is / are undamaged prior to removal thereof.

[0136] 11. A method according to any one of the previous items, wherein the step of removing the one or more blade shell portions includes discarding the one or more removed blade shell portions.

[0137] 12. A method according to any one of the previous items, wherein the airfoil section of the wind turbine blade is continuous.

[0138] 13. A method according to any one of the previous items, wherein the method is performed after completion of manufacturing of the provided wind turbine blade.

[0139] 14. A method according to any one of the previous items, wherein the step of performing a task within the interior of the wind turbine blade via the one or more temporary access windows includes performing one or more of:

[0140] - preferably a method according to any one of items 18-32; retrofitting one or more functional components, such as electrical components, e.g. lightning protection components, sensor components, and heating elements, in the interior of the wind turbine blade; and P2612PC00 (701356-WO-l)

[0141] 21 performing structural repairs, such as bond line repairs, delamination repairs, and crack repairs in the interior of the wind turbine blade.

[0142] 15. A method according to any one of the previous items, wherein the step of irreversibly securing the one or more precured plug components to the blade shell comprises applying a second adhesive to, e.g. a circumference of, the one or more precured plug components, and curing the second adhesive so as to irreversibly secure the one or more precured plug components to the blade shell so as to close the one or more temporary access windows, respectively.

[0143] 16. A method according to any one of the previous items, wherein the one or more plug components is / are a composite material, preferably a composite sandwich material, such as one or more fibre layers on each side of a core material.

[0144] 17. A method according to any one of the previous items further comprising the steps of: recessing, e.g. by grinding, a circumferential portion of the exterior surface of the blade shell at least partly, preferably entirely, around the one or more access windows; and

[0145] - overlaminating one or more layers, such as fibre-reinforced layers, over the respective one or more precured plug components so that the one or more overlaminated layers is / are arranged in recessed portion and substantially flush with the exterior surface of the blade shell.

[0146] 18. A method of repairing a wind turbine blade extending along a longitudinal axis from a root end to a tip end, the wind turbine blade comprising a blade shell forming a profiled contour including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending therebetween, wherein the profiled contour is divided into a root region having a substantially circular or elliptical profile closest to the root end with a root diameter being the chord length at the root end, an airfoil region having a lift-generating profile furthest away from the root end, and a transition region between the root region and the airfoil region, the transition region having a profile gradually changing in the radial direction from the circular or elliptical profile of the root region to the lift-generating profile of the airfoil region, the wind turbine blade further comprises opposing spar caps and one or more shear webs extending along the longitudinal axis, the method comprising the steps of: providing the wind turbine blade, wherein the one or more shear webs includes a first shear web having a damaged portion, and wherein the blade shell of the wind turbine blade comprises one or more access windows providing access to the damaged portion from the exterior of the wind turbine blade; P2612PC00 (701356-WO-l)

[0147] 22 providing one or more fibre-reinforced plates;

[0148] - at the damaged portion, identifying a target area for reinforcement on a side surface of the first shear web; inserting the one or more fibre-reinforced plates having a first adhesive on a first side thereof through the one or more access windows;

[0149] - applying the first side of the one or more fibre-reinforced plates to the target area of the first shear web; and

[0150] - causing or allowing the first adhesive to cure so as to secure the one or more fibre- reinforced plates thereby reinforcing the damaged portion of the first shear web.

[0151] 19. A method according to item 18, wherein the one or more shear webs comprises a second shear web, and wherein the first shear web is arranged towards the trailing edge of the wind turbine blade and the second shear web is arranged towards the leading edge of the wind turbine blade.

[0152] 20. A method according to any one of items 18-19, wherein the one or more fibre-reinforced plates respectively comprises one or more first fibre layers embedded in a first resin.

[0153] 21. A method according to item 20, wherein the one or more first fibre layers comprises a bottom first fibre layer, a top first fibre layer, and one or more intermediate first fibre layers arranged between the bottom fibre layer and the top fibre layer, wherein the extent of the first fibre layers tapers from bottom first fibre layer to the top first fibre layer.

[0154] 22. A method according to item 21, wherein the bottom first fibre layer has the largest extent and each subsequent first fibre layer towards the top first fibre layer has a smaller extent than the previous first fibre layer so that the first fibre layers substantially form a pyramid shape.

[0155] 23. A method according to any one of items 19-22, wherein the first adhesive is different from the first resin of the one or more fibre-reinforced plates.

[0156] 24. A method according to any one of items 19-23, wherein the one or more first fibre layers is / are of the same fibre material as the first shear web.

[0157] 25. A method according to any one of items 18-24, wherein the one or more fibre-reinforced plates is / are precured. P2612PC00 (701356-WO-l)

[0158] 23

[0159] 26. A method according to any one of items 18-25, wherein the target area exceeds or overlaps the damaged portion by a predetermined length and / or predetermined height, preferably the predetermined length being at least 15 mm along the longitudinal axis and / or preferably the predetermined height being at least 15 mm along a thickness direction extending between the opposing spar caps.

[0160] 27. A method according to any one of items 18-26, further comprising cleaning of the target area in preparation for adhesion of the one or more fibre-reinforced plates.

[0161] 28. A method according to any one of items 18-27, wherein the step of identifying a target area for reinforcement further comprises the steps of: measuring the flatness of the target area; and in accordance with a determination that the flatness of the target area exceeds a predetermined threshold, preparing, such as grinding, etc., the side surface of the first shear web at the target area until the flatness of the target area is within the predetermined threshold.

[0162] 29. A method according to item 28, further comprising a step of in accordance with a determination that the flatness of the target area is within a predetermined threshold, forgoing preparation of the side surface of the first shear web at the target area.

[0163] 30. A method according to any one of items 18-29, wherein the step of applying the first side of the one or more fibre-reinforced plates to the target area of the first shear web comprises pressing the first side of the one or more fibre-reinforced plates to the target area of the first shear web using one or more pressure tools so as to apply at least a predetermined pressure for at least a predetermined time period.

[0164] 31. A method according to item 30, further comprising

[0165] - attaching the one or more pressure tools to the blade shell at the one or more access windows; and

[0166] - urging a portion of the one or more pressure tools onto the respective one or more fibre- reinforced plates.

[0167] 32. A method according to any one of items 18-31, further comprising the steps of: P2612PC00 (701356-WO-l)

[0168] 24 providing one or more first fibre-reinforced plates having a first length, and one or more second fibre-reinforced plates having a second predetermined length greater than the first predetermined length; in accordance with a determination that the target area has a length, e.g. along the longitudinal axis, less than or equal to the first predetermined length, selecting a first fibre-reinforced plate for application to the target area; in accordance with a determination that the target area has a length, e.g. along the longitudinal axis, that is greater than the first predetermined length and that is equal to or less than the second predetermined length, selecting a second fibre-reinforced plate for application to the target area; and in accordance with a determination that the length of the target area is greater than the second predetermined length, selecting a combination of one or more first fibre-reinforced plates and / or one or more second fibre-reinforced plates for application to the target area so that the summed length of the selected reinforced plates is equal to or greater than the length of the target area.

[0169] 33. A repaired wind turbine blade obtainable by a method according to any one of the previous items.

[0170] 34. A repaired wind turbine blade extending along a longitudinal axis from a root end to a tip end, the wind turbine blade comprising a blade shell forming a profiled contour including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending therebetween, wherein the profiled contour is divided into a root region having a substantially circular or elliptical profile closest to the root end with a root diameter being the chord length at the root end, an airfoil region having a lift-generating profile furthest away from the root end, and a transition region between the root region and the airfoil region, the transition region having a profile gradually changing in the radial direction from the circular or elliptical profile of the root region to the lift-generating profile of the airfoil region, the wind turbine blade further comprises opposing spar caps and one or more shear webs extending along the longitudinal axis, wherein the one or more shear webs comprises a suction-side web flange attached to a suction-side spar cap, a pressure-side web flange attached to a pressure-side spar cap, and a web panel extending between the suction-side web flange and the pressure-side web flange, wherein the web panel of a first shear web of the one or more shear webs comprises a damaged portion, and wherein the first shear web comprises one or more fibre-reinforced plates adhered to a side surface of the web panel overlapping the damaged portion, preferably so as to reinforce the web panel overlapping the damaged portion. P2612PC00 (701356-WO-l)

[0171] 25

[0172] 35. A kit of parts for repairing a wind turbine blade by a method according to any one of items 1- 32, the kit of parts comprising:

[0173] - one or more fibre-reinforced plates configured for reinforcing a damaged portion of a first shear web of the wind turbine blade; and - one or more precured plug components configured for closing one or more respective temporary access windows of the wind turbine blade.

[0174] 36. A kit of parts according to item 35, further comprising a first adhesive configured for adhering the one or more fibre-reinforced plates to the first shear web of the wind turbine blade.

[0175] 37. A kit of parts according to any one of items 35-36, further comprising one or more pressure tools configured for pressing the one or more fibre-reinforced plates to the first shear web during curing of the first adhesive. 38. A kit of parts according to any one of items 35-37, further comprising a second adhesive configured for irreversibly securing the one or more precured plug components in the respective one or more temporary access windows.

[0176] P2612PC00 (701356-WO-l)

[0177] 26

[0178] LIST OF REFERENCES

[0179] 2 wind turbine 44' second pressure side web flange

[0180] 4 tower 45' second suction side web flange

[0181] 6 nacelle 46' second web panel

[0182] 8 hub 50 first temporary access window

[0183] 10 blade 50L first length

[0184] 13 shell 52 first perimeter

[0185] 14 blade tip 53 first lip

[0186] 15 tip end 54 first recessed circumferential portion

[0187] 16 blade root 55 overlaminated layer

[0188] 17 root end 50' second temporary access window

[0189] 18 leading edge 50L' second length

[0190] 20 trailing edge 52' second perimeter

[0191] 21 root segment 58 chordwise distance

[0192] 22 tip segment 60 first fibre-reinforced plate

[0193] 23 chordwise joint 60L First predetermined length

[0194] 24 pressure side shell part 60' second fibre-reinforced plate

[0195] 26 suction side shell part 60L' second predetermined length

[0196] U exterior blade surface 61 bottom first fibre layer

[0197] 30 root region 62 intermediate first fibre layer

[0198] 32 transition region 63 top first fibre layer

[0199] 34 airfoil region 64 first adhesive

[0200] 36 tip region 70 precured plug component

[0201] 38 shoulder 71 fibre layer

[0202] 40 beam structure 72 core material

[0203] 41 suction side spar cap 74 second adhesive

[0204] 42 pressure side spar cap 80 target area

[0205] 43 first shear web 80L length

[0206] 44 first suction side web flange 80T thickness

[0207] 45 first pressure side web flange 90 pressure tool

[0208] 46 first web panel L longitudinal axis

[0209] 47 side surface T thickness direction

[0210] 48 damaged portion C chordwise direction

[0211] 48L length

[0212] 48T thickness

[0213] 43' second shear web

Claims

P2612PC00 (701356-WO-l) 1CLAIMS1. A method of accessing the interior of a wind turbine blade extending along a longitudinal axis from a root end to a tip end, the wind turbine blade comprising a blade shell forming a profiled contour including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending therebetween, wherein the profiled contour is divided into a root region having a substantially circular or elliptical profile closest to the root end with a root diameter being the chord length at the root end, an airfoil region having a lift-generating profile furthest away from the root end, and a transition region between the root region and the airfoil region, the transition region having a profile gradually changing in the radial direction from the circular or elliptical profile of the root region to the lift-generating profile of the airfoil region, the wind turbine blade further comprises opposing spar caps and one or more shear webs extending along the longitudinal axis, the method comprising the steps of: providing the wind turbine blade;- from the exterior of the wind turbine blade, removing one or more blade shell portions of the blade shell in the airfoil region of the blade shell of the wind turbine blade at a chordwise distance from the opposing spar caps so as to establish one or more respective temporary access windows for an operator to the interior of the wind turbine blade; performing a task within the interior of the wind turbine blade via the one or more temporary access windows;- from the exterior of the wind turbine blade, inserting one or more precured plug components in the one or more temporary access windows, respectively; and- irreversibly securing the one or more precured plug components to the blade shell so as to close the one or more temporary access windows.

2. A method according to claim 1, wherein the method is performed up-tower.

3. A method according to any one of the previous claims, wherein the respective one or more temporary access windows comprises one or more lips extending at least partly, preferably entirely, around a perimeter of the respective one or more temporary access windows, and wherein the step of inserting one or more precured plug components in the one or more temporary access windows, respectively, includes resting the one or more precured plug components on the respective one or more lips of the one or more access windows.

4. A method according to any one of the previous claims, wherein the one or more blade shell portions is / are undamaged prior to removal thereof.P2612PC00 (701356-WO-l)285. A method according to any one of the previous claims, wherein the step of removing the one or more blade shell portions includes discarding the one or more removed blade shell portions.

6. A method according to any one of the previous claims, wherein the airfoil section of the wind turbine blade is continuous.

7. A method according to any one of the previous claims, wherein the method is performed after completion of manufacturing of the provided wind turbine blade.

8. A method according to any one of the previous claims, wherein the step of performing a task within the interior of the wind turbine blade via the one or more temporary access windows includes performing one or more of: preferably a method according to any one of claims 10-12; retrofitting one or more functional components, such as electrical components, e.g. lightning protection components, sensor components, and heating elements, in the interior of the wind turbine blade; and performing structural repairs, such as bond line repairs, delamination repairs, and crack repairs in the interior of the wind turbine blade.

9. A method according to any one of the previous claims further comprising the steps of: recessing, e.g. by grinding, a circumferential portion of the exterior surface of the blade shell at least partly, preferably entirely, around the one or more access windows; and- overlaminating one or more layers, such as fibre-reinforced layers, over the respective one or more precured plug components so that the one or more overlaminated layers is / are arranged in recessed portion and substantially flush with the exterior surface of the blade shell.

10. A method of repairing a wind turbine blade extending along a longitudinal axis from a root end to a tip end, the wind turbine blade comprising a blade shell forming a profiled contour including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending therebetween, wherein the profiled contour is divided into a root region having a substantially circular or elliptical profile closest to the root end with a root diameter being the chord length at the root end, an airfoil region having a lift-generating profile furthest away from the root end, and a transition region between the root region and the airfoil region, the transition region having a profile gradually changing in the radial direction from the circular or elliptical profile of the root region to the lift-generating profile of the airfoil region, the wind turbine blade furtherP2612PC00 (701356-WO-l)29 comprises opposing spar caps and one or more shear webs extending along the longitudinal axis, the method comprising the steps of: providing the wind turbine blade, wherein the one or more shear webs includes a first shear web having a damaged portion, and wherein the blade shell of the wind turbine blade comprises one or more access windows providing access to the damaged portion from the exterior of the wind turbine blade; providing one or more fibre-reinforced plates;- at the damaged portion, identifying a target area for reinforcement on a side surface of the first shear web; inserting the one or more fibre-reinforced plates having a first adhesive on a first side thereof through the one or more access windows;- applying the first side of the one or more fibre-reinforced plates to the target area of the first shear web; and- causing or allowing the first adhesive to cure so as to secure the one or more fibre- reinforced plates thereby reinforcing the damaged portion of the first shear web.

11. A method according to claim 10, wherein the step of applying the first side of the one or more fibre-reinforced plates to the target area of the first shear web comprises pressing the first side of the one or more fibre-reinforced plates to the target area of the first shear web using one or more pressure tools so as to apply at least a predetermined pressure for at least a predetermined time period.

12. A method according to any one of claims 10-11, further comprising the steps of: providing one or more first fibre-reinforced plates having a first length, and one or more second fibre-reinforced plates having a second predetermined length greater than the first predetermined length; in accordance with a determination that the target area has a length, e.g. along the longitudinal axis, less than or equal to the first predetermined length, selecting a first fibre-reinforced plate for application to the target area; in accordance with a determination that the target area has a length, e.g. along the longitudinal axis, that is greater than the first predetermined length and that is equal to or less than the second predetermined length, selecting a second fibre-reinforced plate for application to the target area; and in accordance with a determination that the length of the target area is greater than the second predetermined length, selecting a combination of one or more first fibre-reinforced plates and / or one or more second fibre-reinforced plates for application to the target areaP2612PC00 (701356-WO-l)30 so that the summed length of the selected reinforced plates is equal to or greater than the length of the target area.

13. A repaired wind turbine blade obtainable by a method according to any one of the previous claims.

14. A repaired wind turbine blade extending along a longitudinal axis from a root end to a tip end, the wind turbine blade comprising a blade shell forming a profiled contour including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending therebetween, wherein the profiled contour is divided into a root region having a substantially circular or elliptical profile closest to the root end with a root diameter being the chord length at the root end, an airfoil region having a lift-generating profile furthest away from the root end, and a transition region between the root region and the airfoil region, the transition region having a profile gradually changing in the radial direction from the circular or elliptical profile of the root region to the lift-generating profile of the airfoil region, the wind turbine blade further comprises opposing spar caps and one or more shear webs extending along the longitudinal axis, wherein the one or more shear webs comprises a suction-side web flange attached to a suction-side spar cap, a pressure-side web flange attached to a pressure-side spar cap, and a web panel extending between the suction-side web flange and the pressure-side web flange, wherein the web panel of a first shear web of the one or more shear webs comprises a damaged portion, and wherein the first shear web comprises one or more fibre-reinforced plates adhered to a side surface of the web panel overlapping the damaged portion, preferably so as to reinforce the web panel overlapping the damaged portion.

15. A kit of parts for repairing a wind turbine blade by a method according to any one of claims 1-12, the kit of parts comprising:- one or more fibre-reinforced plates configured for reinforcing a damaged portion of a first shear web of the wind turbine blade; and- one or more precured plug components configured for closing one or more respective temporary access windows of the wind turbine blade.

Images